1. Field of the Invention
This invention relates to a semiconductor device, and more particularly to a method for forming an SOI(Silicon On Insulator) structured substrate suitable for a high speed device.
2. Discussion of the Related Art
Conventional methods for forming an SOI structured substrate such as, the SIMOX(Silicon Implanted Oxygen), SDB(Silicon Direct Bonding), and recrystallization by a strip heater are known widely.
The SIMOX method involves forming the SOI structured substrate by forming an oxide film on a surface of a silicon substrate with high energy injection of oxygen ions into the silicon substrate. The oxygen ions are coupled with the silicon ions upon heating them at a high temperature.
The SDB method involves forming the SOI structured substrate by bonding a silicon substrate on another silicon substrate on which an oxide film has been formed. This surface has been polished such that it has no dangling bonding.
The recrystallization by a strip heater method involves forming the SOI structured substrate by recrystallizing a polycrystalline silicon film into a single silicon, crystal. In this method, the polycrystalline silicon film is deposited on an oxide film formed on a silicon substrate which has been melted starting at a side thereof scanned by a halogen lamp.
However, the foregoing methods have the following problems.
Due to the high energy injection of oxygen ions into the silicon substrate, the SIMOX method damages the surface of the silicon substrate and consequently degrades the properties of the interface between the silicon substrate and the oxide film. Due to bonding of the two substrates, the SDB method has problems of being liable to form voids at the bond between the two substrates, and of having to polish the substrate many times after the bonding of the substrates. The recrystallization by a strip heater method has a problem of poor crystallization due to recrystallization into a single crystal after melting the polycrystalline silicon film.